This invention relates, generally, to cranes and relates more particularly, to support or stowing apparatus for stowing the boom of a crane in an elevated or raised position.
The type of crane with which this invention is concerned includes a frame, an upwardly-projecting mast rotatably mounted on the frame, and a boom secured to the free end of the mast. Such cranes are commonly mounted on a vehicle such as a semitrailor tractor truck.
The stowing apparatus with which this invention is concerned includes a pair of props or leg members adapted to extend between the crane boom and the crane frame. Extending therebetween, the props support the free end of the boom at a minimum elevation and prevent the boom from swaying from side to side while the crane is being transported. In applications in which the crane is mounted directly behind a truck cab, the stowing apparatus is advantageous in that it consumes no valuable space, for example, on the bed of the truck. Such a stowing apparatus is shown and described in U.S. Pat. No. 3,792,778.
A boom stowing apparatus, such as the one described in the referenced patent, includes no means for preventing the free end of the boom from moving upwardly relative to the crane frame. Instead, such upward movement of the free end of the boom is prevented only by the weight of the boom upon the apparatus props. Upward jarring of the boom, such as may be experienced while the crane is being transported between job sites, could cause the boom to bounce off of the stowing props. Furthermore, such an apparatus requires that its props be manually lifted in order to place the props into or out of a boom-stowing condition. The props of such an apparatus are relatively heavy and can, consequently, be very difficult to lift manually. Still further, props of such an apparatus are stored, when not in use, alongside the crane frame. In applications requiring that the crane boom operator stand alongside the crane frame while manipulating the boom controls, the stored props are likely to be in the operator's way. Yet still further, such an apparatus is relatively complicated in structure and, thus, relatively costly to manufacture.
It is, accordingly, an object of the present invention to provide a new and improved crane boom stowing apparatus which securely locks the boom at an elevated position and thereby prevents the free end of the boom from moving upwardly or downwardly relative to the crane frame.
Another object of the present invention is to provide such a boom support assembly which is easy to use and requires no manual lifting of heavy members when placing the apparatus in a boom-stowing condition or an apparatus-storing condition.
Still another object of the present invention is to provide such a boom support apparatus which is storable in a condition so that it cannot interfere with the manipulations of a crane boom operator.
Yet still another object of the present invention is to provide such a boom support assembly which is uncomplicated in structure and relatively economical to manufacture.